A conventional projection-type display apparatus such as an apparatus whose display device is made using a liquid-crystal panel is configured in such a way that, after light radiated from a light-source lamp and reflected by a reflector has been separated into predetermined colored light segments through a plurality of dichroic mirrors, and then each of the segments is made incident on the liquid-crystal panel segments corresponding to R, B, and G, through a polarizing beam splitter, to be modulated with imaging signals, etc., each of the segment is focused through another dichroic mirror and a dichroic prism, and projected onto a screen through a projection lens.
As described above, the projection-type display apparatus is structured by including, for example, a case for housing therein a display device composed of a light source lamp, optical parts, and a liquid crystal panel, a control board for controlling image data, and an electric-power board, and a projection lens provided on the front of this case. Moreover, when the apparatus is not operated, in order to protect the projection lens or prevent accumulation of dust, a lens cap is provided on the projection lens or a cover is placed upon the lens; therefore, if electric power is applied, and light radiated from the light-source lamp with the lens cap or the cover being placed thereupon, the light outputted through the projection lens is projected to the lens cap or the cover, and due to heat from the light, not only the lens cap or the cover is deformed, but also the temperature inside the apparatus increases; consequently, a problem has occurred in which the lifetime of the projection-type display apparatus is shortened.
In order to overcome this problem, apparatuses are disclosed that detects the lens cap being placed, and then, shuts down the lamp source (for example, refer to Patent Document 1), and in which an electric-power-source inlet is arranged dose to the projection lens so as not to supply electric power thereto when the lens cap is placed (for example, refer to Patent Document 2).
However, projection-type display apparatuses have proliferated which have functions in which an operation is performed while looking at a menus projected on the screen, when setting states of the apparatus are checked or changed, especially, in more recent sophisticated-and-multifunctional displays. Therefore, lamps for the light sources tend to be used so much used even when the set does not display a broadcast or playback image.
[Patent Document 1] Japanese Laid-Open Patent Publication 112,029/2000 (FIG. 1, FIG. 2)
[Patent Document 2] Japanese Laid-Open Patent Publication 344,848/2002 (FIG. 1)